ever wanted to have a powerful speaker system for those inpromtue garden parties/field raves. many will say this is a redundant Instructable, as there are many boombox style radios from days gone by cheaply available, or these cheap ipod style mp3 docking stations that run on batteries.
I strongly disagree with this statement, boomboxes are huge and eat batteries, docking stations are weak and sound poor. so for the best of both worlds, I present to you my portable rave speakers.
I built these speakers to meet these specifications:
-compact, for easy, in a back pack transport
-powerful, for punchy clear audio to get those outdoors raves going
-long run time, who wants to stop raving ?
First step as always is, what do you need?
-speaker cones (take them out of a couple of sets of computer speakers)
-amplifier chip (see next step for details)
-3.5mm audio jack
-2 * 470nf capacitors
- a 220 micro F capacitor
-2 5kohm resistors
-high capacity set of batteries (12-18v 4000mah+)
-the best heatsink you gan get
-dremel (or equivalent)
-lots of assorted shrink tubing (electrical insulation)
-small project box (altiods tin would suffice)
-a good length of good quality wire.
-battery connectors of choice (I chose deans "t" connectors)
Step 2: Chosing the Right Combination of Components
this step is to ensure that you don't go and buy components that are mis-matched.
the first thing that I found were the cones, I found these laying around my house. once you have your speakers open them up to see the cones themself, they should have a power rating and a resistance printed on the back, take note of these.
with the rating on the back of the speakers choose an appropriate amplifier chip, for me I had lot of 4 3.6W 4ohm cones, I decided to put them into two series connected sets, this gave me two satellite speakers each with a rating of 7.2W and 8ohms, the chip I found to match this was the TDA7057AQ, a quick search on farnell/digikey will find one to match your cones.
The amplifier chip will have a maximum input voltage in the data sheet, find the largest capacity battery you can that conforms to these voltage limits, I went with two 4 cell lipo batteries each with a capacity of 2250mAh wired in parallel to make a 4 cell pack with capacity 4500mAh
now you have all the major components worked out you can start the build.
Step 3: Start the Building
ok below is the schematic that i followed for the chip stated erlier, a simple schematic will be included in the datasheet of the amplifier you purchased (the schematic posted hear was not done by me it was in the datasheet)
start making the relevant connections to the chip, i would reccomend measuring the size of your project box so that you dont make the connecting wires obsesivly short or long. make all of the connections to the chip first so that a length of shrink tubing can be sliped on from the unsoldered side of the wire (this way ensures that the pins on the chip are all well insulated, as this is the biggest concern for shorting as the pins can be very close together)
after all your wires are connected to the chip and the heat shrink is shrunk, connect the external components, i used a copper strip board piece to organise the small number of capacitors needed for this circuit, a neat job will help prevent accidental shorts. make sure the wires connecting the potentiometer are of a length that permits a comfortable mounting within the box.
Step 4: Making the Amplifier Housing
In the project box that you have you will need to mark out a section to be cut out to allow the chip heatsink to pertrude. A hole for the potentiometer to pertrude and holes for the jack wire speaker wires and the power cables. For the cable holes use a drill with a 4mm bit, for the heatsink the best tool is a dremel type tool with one of the reddish thin cutting disks, around the heatsink hole you will also need to drill a couple of holes for bolts to secure the heatsink.
Step 5: Making the Speakers
The method i used to produce the speakers was very simple, cutting 4 strips of aluminium with the demel and drilling holes in ether end of each so that i could bolt a pair of cones inbetween two strips of aluminium, this holds the cones secure enough, and it has a kind of minimalism about it.
Step 6: Connect the External Connectors and Attach the Heatsink
run the appropriate cables throutgh the appropriate holes and solder on the connectors, the 3.5mm headphone jack and the deans "t" power connectors. Also connect the speaker wires to the speakers.
The last part of amplifier assembly is to drill a pair of holes in the heatsink rouhgly in the middle to recieve the chip, apply some thermal paste inbetween the chip and the heatsink and bolt the chip to the heatsink through the mounting holes. bolt the heatsink to the case.
Step 7: Connect Mp3 Player and Test
Apply power to the power leads and plug in the 3.5mm jack making sure that the volume on the mp3 player is on minimum, increase the volume a small amount on the mp3 player, so that you can hear quiet music then on the potentiometer find which way is volume up and which is volume down. Next slowly increase the volume on the mp3 player and on the potentiometer so that when the mp3 player is on maximum volume the speakers are as loud as you dare go! (if they are starting to distort that is loud enough).
Step 8: Box It Up
This step is more of a convenience as hopefully your speakers are already working! I found a cardboard box that looked to be the right size to house everything, it was an ex-computer game box as far as I know, but it is plane white. put the lid on the box and make some box strapping out of some long zip ties (these stop the box opening unnecessarily on your travels)
Step 9: Rave It Up
Get raving! the speakers can be used whilst they are still in the box for convenience or the speakers removed for improved stereo sound.
Now you can throw these in your bag on your travels and you will have over 6 hours of playtime on full volume (yes I have done run time test )
6 hours - that sure does beat the 1.5 hours supplied by my old boom box with an unreasonable amount of d cell batteries, and mine can be recharged thousands of times!